1. Field of the Invention
The present invention relates generally to a paste sector for applying paste in a predetermined pattern to an item being manufactured, such as to the inner and outer bottom flaps of bags disposed on the drum of a bag making machine.
More particularly, the invention relates to a paste sector for disposal on a paste sector shaft of a bottom pasting station of a bag making machine. The paste sector shaft with the paste sector disposed thereon cooperates with an assembly which provides a paste film to the paste sector, and the paste sector in accordance with the invention in turn effectively applies a film of paste to the open bottom of a paper bag as the partially formed bag passes through the bottom pasting station of the bag making machine.
2. Description of Relevant Art
In the manufacture of paper bags, there is known a variety of different types of bag making machines which form conventional paper bags from a sheet of paper dispensed from a large paper roll. Various operations are performed on the paper as it passes through a plurality of stations including sequentially, for example, a tube forming station, a score station, a cutting and bottom portion opening station, and a bottom forming station. Normally, after the bag bottom formation is completed in the bottom forming station, the bottom portion of the bag is flattened against the forming drum of the bag making machine, and the partially formed bag is then conveyed by the drum to a bottom pasting station.
The bottom pasting station of the bag making machine may comprise, for example, a paste sector mounted on a paste sector shaft, which shaft is geared to the forming drum of the bag making machine, and may be mounted on bearing blocks which are spring loaded toward the forming drum of the machine. A lever and cam arrangement may be provided for selective lifting of the paste sector away from the drum surface when it is desired to withhold paste application to the open bottoms of the partially formed bags.
Operatively cooperating with the paste sector and shaft is an assembly for providing a paste film to the paste sector itself, which in turn applies a film of paste to the open bottom of the partially formed bag. Such assembly may comprise, for example, a pan for containing the substantially low viscosity paste, a metal applicator roll which may be geared to the paste sector shaft and which is loaded with paste about its periphery from the open pan of paste, and a doctor member which cooperates with the applicator roll to permit a predetermined thickness of paste to pass from the applicator roll to the paste sector.
When the partially formed bag, flattened against the forming drum such that the flaps of the open bottom of the bag are positioned to be engaged by the paste sector, is received in the bottom pasting station, the paste sector is rotated against the paste applicator roll so as to transfer a film of paste of desired thickness from the applicator roll to the open bottom flaps of the bag.
After application of the paste to the open bottom of the bag in the bottom pasting station as described hereinabove, the partially formed bag then passes through several more stations wherein final cutting, tucking, bottom closing, and various other operations may be effected, until the finally formed bag is ultimately delivered to the final station of the bag making machine, such as a delivery table.
The conventional paste sector employed in the bottom pasting station as described hereinabove is normally formed of metal, such as brass. The paste sector includes a raised paste-applying surface portion, which may for example be corrugated, for applying the paste in a predetermined pattern to the open bottom flaps of the bag being formed. Such known paste sectors, however, have a number of serious shortcomings and disadvantages attendant therewith.
Due to the rigidity of the material from which the paste sectors are formed, viz., brass, it is necessary to employ sponge rubber mountings, or alternatively a hinge arrangement, in order to compensate for variation in the thickness of the open bottom of the bags being formed. Such sponge rubber mounting of the paste sectors tends to lead to instability during operation. Further, the paste applicator roll against which the paste sector is rotated during the paste application procedure is normally itself formed of metal, such as brass. The repeated rotational contact of the paste sector against the brass surface of the applicator roll has a tendency to cause excessive wear to the brass paste sectors, and a deteriorating effect on the paste sectors results. Yet another shortcoming of the known paste sector construction is the small holes necessarily formed therein during fabrication to permit bolting of the metal paste sector to a mandrel for machining purposes, and for ultimately mounting the paste sectors on pins during use.
Illustrative of a known adhesive applying device is the "ADHESIVE APPLYING DEVICE" disclosed in U.S. Pat. No. 1,851,761 issued in 1932 to Everett. Such device includes rollers for applying adhesive which may be employed with sodium silicate, which is quite different to remove when dry from metal or wood rollers. The rollers are provided with tubular covers formed from a cementitious material such as phenolic resin and a filler, with the outer portion comprising a layer of unfilled cementitious material. Only the outer portion of the metallic rollers is non-metallic, with the surfaces being formed of a smooth, hard material such as phenolic.
Illustrative of a known bottom paste applying arrangement for bag making machines is the "LOW VISCOSITY BOTTOM PASTE APPLICATOR FOR BAG MACHINES" disclosed in U.S. Pat. No. 3,450,099 issued in 1969 to Petersen. In such arrangement, paste is applied to paste sectors using a metering pump to apply paste to a transfer roll, and a doctor blade to concentrate paste to the area of the transfer roll which contacts the paste sector. The paste sector employed in such arrangement is of a conventional construction.
Yet another adhesive applying device is illustrated by the "APPLICATOR ROLL" disclosed in U.S. Pat. No. 3,529,336 issued in 1970 to Winkler et al. Such device comprises an applicator for applying latex to self-sealing bags or envelopes. The applicator is formed by a strip of soft embossed polyvinyl chloride mounted to a gumming cylinder. The polyvinyl chloride is employed due to its resistance to being attacked by latex, contrary to rubber material. The polyvinyl chloride is soft, and conventional glue will not adhere thereto.
The above-discussed known adhesive applying constructions have failed individually and collectively to provide any solution to the problems attendant the paste sectors of known construction as described hereinabove.
The present invention is directed to effectively eliminating the various shortcomings and disadvantages attendant known paste sectors as described hereinabove. The paste sector according to the present invention eliminates the need for any special sponge rubber mounting or hinge arrangement to accommodate variations in thickness, thus greatly enhancing stability during operation. Further, the paste sector in accordance with the present invention easily accommodates irregularities, is highly wear-resistant even after repetitive use while bearing against a metal paste applicator roll, and does not require the formation of holes therein during fabrication thereof.